1. Field of the Invention
The present invention relates to an optical disc device that finds an optimum recording power when data is written in a data area by writing data for calibration to the power calibration area of an optical disc, and in more detail, to an optical disc device in which a method for acquiring an optimum recording power when an area to be written is a not-yet-recorded area is different from a method for acquiring an optimum recording power when an area to be written is an already recorded area.
2. Description of the Related Art
When data is written to a rewritable optical disc such as a DVD-RW, an optimum recording power at the time of recording data is found before writing data. That is, data is written for calibration to a power calibration area (PCA) while changing laser power and an optimum recording power used for recording data is found from the reproducing signal of data written for calibration. However, an optimum recording power is different between a case where an area in which data is to be written is an area in which data has not yet recorded and a case where an area in which data is to be written is an area in which data has been already written. Then, in a case where an area in which data is to be written is an area in which data has been already written, an optimum recording power is also different depending on the intensity of laser power used for writing data. For this reason, there has been proposed the technology to be described below.
That is, in this technology, it is checked whether an area in which data is to be recorded is a not-yet-recorded area or an already recorded area in which data has been already recorded. Then, when an area in which data is to be recorded is a not-yet-recorded area, data is written for calibration to a power calibration area while changing the intensity of a recording laser power stepwise and finds an optimum recording power from the waveform of the reproducing signal of data written for calibration and then records data by using the found optimum recording power, whereas when an area in which data is to be recorded is an already recorded area, just as with the case of the not-yet-recorded area, an optimum recording power is found by using a power calibration area and the already recorded area is reproduced and the demodulation degree Mopt of the already recorded area is found from a reproducing signal at that time and then the found modulation degree Mopt is compared with a modulation degree Mtarget that has been previously set for each device.
As a result of comparison, when it is determined that the modulation degree Mopt of the already recorded area is larger than the modulation degree Mtarget that has been previously set for the device, data is written by using a laser power a little smaller than an optimum recording power found by using a power calibration area. Meanwhile, when it is determined that the modulation degree Mopt of the already recorded area is equal to the modulation degree Mtarget that has been previously set for the device, data is written by using the optimum recording power found by using a power calibration area. Then, when it is determined that the modulation degree Mopt of the already recorded area is smaller than the modulation degree Mtarget that has been previously set for the device, data is written by using a laser power a little larger than the optimum recording power found by using a power calibration area.
In other words, when date is overwritten in an already recorded area, a laser power when data has been written in the already recorded area is detected as a modulation degree. Then, the optimum recording power found by using a power calibration area is corrected on the basis of a detected laser power and data is overwritten in the already recorded area by using the corrected optimum recording power. That is, the laser power when data has been overwritten in the already recorded area is corrected according to the state of the already recorded area. For this reason, it is possible to prevent a laser power from being insufficient at the time of writing data or from being unnecessarily intensive. Hence, there is provided an advantage that the reliability of writing data can be improved without damaging the durability of an optical disc (refer to, for example, JP-A-2003-99933 (paragraph No. 0015)).
However, there have been raised problems shown below at the time of using the above-mentioned conventional technology. That is, even if laser power for writing is finely adjusted according to a comparison result between the modulation degree of an already recorded area and a modulation degree previously set for each device, the finely adjusted laser power becomes only a value considered to be optimum from previously obtained experimental data. That is, the finely adjusted laser power does not become a laser power corresponding to the state at that time of the already recorded area of an optical disc to which data is to be written or the state at that time of an optical pickup (ambient temperature and the like). For this reason, there is a case where laser power used for writing data to an already recorded area and having its intensity finely adjusted is deviated from an optimum value and hence there are sometimes presented the problem of reducing the reliability of written data and the problem of causing the life of the optical disc to be unnecessarily short.
The present invention has been made to solve the above problems. An object of the present invention is to provide an optical disc device that can record data by using a recording laser power to make an actually reproduced signal an optimum signal in both cases of a case where an area to be written is a not-yet-recorded area and a case where an area to be written is an already recorded area, and can make a recording laser power an optimum value for each data area even when an area to be written includes areas in which data has been written by recording laser powers that are different from each other, and can eliminate the need for additionally providing the function of causing the device to be more complex such as storing means for storing much laser power information and managing means for managing laser power information, and can write data continuously without interruption even when an area to be written includes areas in which data has been written by using recording laser powers that are different from each other and recording laser powers are made optimum values for the respective areas.
Moreover, another object of the present invention is to provide an optical disc device that finds an optimum recording power by using a not-yet-used power calibration area in a case where an area to be written, which is an area in which data is to be written, is a not-yet-recorded area, and writes preliminary data to a power calibration area by using a recording laser power used for writing data to an area to be written and then finds an optimum recording power by using a power calibration area in which preliminary data has been written in a case where an area to be written is an already recorded area, thereby being able to record data by using a recording laser power to make an actually reproduced signal an optimum signal in both cases of the case where an area to be written is a not-yet-recorded area and the case where an area to be written is an already recorded area.
Then, in addition to the above-mentioned object, still another object of the present invention is to provide an optical disc device that writes data by using an optimum recording power corresponding to each data area in which data is to be written when an area to be written includes data areas in which data has been written by using recording laser powers that are different from each other, thereby being able to make a recording laser power an optimum value for each data area even when an area to be written includes data areas in which data has been written by using recording laser powers that are different from each other.
Then, in addition to the above-mentioned object, still another object of the present invention is to provide an optical disc device that records laser power information, which is information that makes a recording laser power when data is written in a data area correspond to the data area, in a specified area of an optical disc to eliminate the need for providing storing means for storing laser power information for each optical disc in a device, thereby being able to eliminate the need for additionally providing the functions of making the device more complex such as storing means for storing much laser power information and managing means for managing laser power information.